8AM isn't a particularly horrible time to arrive EZE (a bit later can be) - I'd expect that you'll be done with all of your arrival tramites within 45 minutes of getting off the plane.

Are you on 1 ticket? Your bag might already be tagged, so your AR check-in/bag drop off will be a bit faster. You should arrive in A, and depart from C. The only priority in that airport is the priority that the terminal be torn down and rebuilt.

From what I've heard, the VIP arrival service on a great day isn't worth $50, let alone $250.